Vegetative propagation of selected clones of cocoa (Theobroma cacao L.) by stem cuttings

The government of Cameroon is responsible for distributing hybrid cocoa seeds to farmers in Cameroon. These high-yielding and pod rot-resistant hybrids are obtained from self-incompatible commercial clones used for seed production by manual pollination of freshly opened flowers. The experimental procedure for the propagation technique of these clones has never been reported. The objectives of this study are to assess the effect of clone, cutting source and growth regulator concentration on the growth and rooting of cocoa (Theobroma cacao L.) stem cuttings. The experiment consisted of 4 clones (SNK16, ICS40, UPA143 and T79/501; two cutting sources: B1 = orthotropic and B2 = Plagiotropic) and four concentrations of growth regulator (4-indol-3-butyric acid) concentrations (D0 = 0 mg, D1 = 12.5 mg, D2 = 25 mg and D3 = 37.5 mg), thus a 4 × 2 × 4 factorial experiment in a completely randomized block design with 3 replicates was designed. Cuttings were set and monitored weekly for shoot sprouting for 10 weeks and rooting at the 10th week. The following parameters were measured: survival rate, number of cuttings with shoots, number of produced shoots, leaves length, number and length of produced roots. Clone, cutting source and growth regulator concentration significantly affected survival rate, shoot sprouting and rooting of cocoa cuttings at p = 0.05. Overall, cuttings started producing shoots 3 weeks after setting (WAS) and at 10 WAS all the cuttings had rooted. Assessment of cuttings in Clementine propagators showed a survival rate of approximately 75%, with orthotropic cuttings showing higher results than plagiotropic cuttings, whereas, D1 (12.5 mg) was the overall effective growth regulator (IBA) concentration that induced the highest number of roots from all the clones. UPA143 was the clone with highest value for all the factors assessed. The results will be valuable in management decision when producing planting materials by stem cuttings.  Key words: Theobroma cacao, vegetative propagation, clone, cutting source, growth regulator concentration, clementine propagator, shoot and root growth.